Two 100 TeV Neutrinos Coincident with the Seyfert Galaxy NGC 7469
Giacomo Sommani, A. Franckowiak, Massimiliano Lincetto, R.‐J. Dettmar
Abstract
Abstract In 2013, the IceCube collaboration announced the detection of a diffuse high-energy astrophysical neutrino flux. The origin of this flux is still largely unknown. The most significant individual source is the close-by Seyfert galaxy NGC 1068 at the 4.2 σ level with a soft spectral index. To identify sources based on their counterpart, IceCube releases real-time alerts corresponding to neutrinos with a high probability of astrophysical origin. We report here the spatial coincidence of two neutrino alerts, IC 220424A and IC 230416A, with the Seyfert galaxy NGC 7469 at a distance of 70 Mpc. We evaluate, a posteriori, the chance probability of such a coincidence and discuss this source as a potential neutrino emitter based on its multiwavelength properties and in comparison to NGC 1068 by performing a goodness-of-fit test. A test statistic is derived from a likelihood ratio that includes the neutrino angular uncertainty and the source distance. We apply this test first to a catalog of active galactic nucleus sources and second to a catalog of Seyfert galaxies only. Our a posteriori evaluation excludes the possibility of an accidental spatial coincidence of both neutrinos with the Seyfert galaxy NGC 7469 at the 3.2 σ level, leaving open the possibility that either one or both neutrinos originated from the source. To be compatible with nondetections of TeV neutrinos, the source would need to have a hard spectral index.